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PostPosted: Tue Nov 29, 2005 3:16 pm 
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Thomas, Winch et al, while I'm not a "math wiz" (see sig), I would be interested in anyone here's opinion of the announcement in 2003 that Gravity's speed is equal to .95 of "c" (although with a large error factor of +/-25%). Winch points to a site regarding the opinion of Tom Van Flandern who calculates that the bottom speed of Gravity is at least 20 billion times "c" (which I find fascinating, as it supports FTL). I kept poking about the web, and found a cadre of diciples to that belief.

It seems that if Gravity is about the same as "c", String theory and multiple universes lose much of their foundation (like that matters, maybe). I found an interesting bunch of sites about Lorentz, which point to mistakes in Einstein's math (!). Then I found a paper that the author's theory called a "Triangle of Velocities", that says both Lorentz's and Einstein's math were flawed :roll: . This last one is a very current paper (Nov. 2005). I just find it interesting that for supposedly being so perfect, mathematics seems more and more like politics to me :wink: . While I'm not trying to ignite something, I am trying to see how close Mr. Weber's PSB is to what we know currently (if that's even possible).

Some sites that report Gravity's speed at about "c" m/l:

http://math.ucr.edu/home/baez/physics/R ... speed.html
http://www.newscientist.com/article.ns?id=dn3232

Some sites that like "fast" Gravity:

http://www.gravitywarpdrive.com/Rethink ... tivity.htm
http://www.metaresearch.org/cosmology/g ... _limit.asp

Here's the guy (He's a Serbian I think) that says Lorentz and Einstein are both wrong :wink: :

http://www.masstheory.org/

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PostPosted: Tue Nov 29, 2005 7:34 pm 
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Darell C. Phillips wrote:
Thomas, Winch et al, while I'm not a "math wiz" (see sig), I would be interested in anyone here's opinion of the announcement in 2003 that Gravity's speed is equal to .95 of "c" (although with a large error factor of +/-25%). -- snip--
I just find it interesting that for supposedly being so perfect, mathematics seems more and more like politics to me

Some sites that report Gravity's speed at about "c" m/l:

http://math.ucr.edu/home/baez/physics/R ... speed.html
http://www.newscientist.com/article.ns?id=dn3232

Some sites that like "fast" Gravity:

http://www.gravitywarpdrive.com/Rethink ... tivity.htm
http://www.metaresearch.org/cosmology/g ... _limit.asp

Here's the guy (He's a Serbian I think) that says Lorentz and Einstein are both wrong :wink: :

http://www.masstheory.org/


Well, it is my understanding that the vast majority of physicists are of the opinion that the speed of gravity is no more than c. And I tend to trust the New Scientist website more than a web site called "gravityWarpDrive" :roll:

And while math is perfect, its application is not. Math, like logic, is about the validity of the process. It cannot be used to determine if something is true or false.

Logic states that the following is in proper logical form: if A is equal to B, and B is equal to C, therefore A is equal to C.

So the following is perfectly logical: If women are slaves and Betty is a woman, therefore Betty is a slave. It is also utterly false.

Like they used to say in computer programming: Garbage In, Garbage out.

The way to determine the truth is by the scientific method. Which include doing experiments, like the one Mr. Zebrowski mentioned.


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PostPosted: Wed Nov 30, 2005 12:32 am 
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I suppose if I stir up enough interest, we can dedicate a topic to this subject (I'm assuming the topic owner is also satisfied with his answer to "Grouped Point Defence"). Thank you Winch, and your example was very satisfactory (and well stated for a layman such as I). The thing that bothers me just a bit is that if indeed Gravity is pretty much the same speed as c is, doesn't this contradict instantaneous action at a distance, which seems to be accepted in order to keep the planets in orbit? Keep in mind here just how close my current math knowledge is to my new signature :) (as in, I'm hanging on my words at the end of my fingernails and hoping for a gravity assist). I see Van Flandern's examples and charts for example of "Propagation Delay versus Aberration" and 'Does a Gravitational Field Continuously Regenerate, or is it "Frozen?" ', and as a layman I get this gut feeling that Gravity is much faster than light can possibly be, you know? I guess my question can be boiled down to this: "If we accept that Gravity is the same speed as Light, does this new information upset any current notions about Planetary orbits and related understandings?"

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PostPosted: Wed Nov 30, 2005 1:22 am 
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Technically, changes in a gravitational field propagate at c; the gravitational field itself has no speed. What this means is, if the sun somehow vanished, it would take 8 minutes before the earth stopped falling towards where the sun used to be.

This doesn't affect orbital calculations any more than electromagnetic fields moving at c changes the logic for electrostatic attraction.


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PostPosted: Wed Nov 30, 2005 2:02 am 
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Anthony Jackson wrote:
Technically, changes in a gravitational field propagate at c; the gravitational field itself has no speed. What this means is, if the sun somehow vanished, it would take 8 minutes before the earth stopped falling towards where the sun used to be.

This doesn't affect orbital calculations any more than electromagnetic fields moving at c changes the logic for electrostatic attraction.


What you are saying is that Gravity is then treated the same as Light. If someone plucked the Sun away, the light would cease (from our point of view) at the same instant that the Earth started moving in a straight line. I guess I was thinking that Gravity would be faster off the mark than Light (too many years reading Sci-Fi, lol). I still wish there was some way to break through "Einstein's Wall". I wrote some space combat rules over a decade back where I had my fleets jumping through wormholes. Up until the discovery by Mankind of this method of escaping our solar system, I stated how ironic that our local Star was named "Sol", which some smartass (that would be me of course) explained it as the acronym S.O.L.- "S__t Outta Luck" :roll: . Thanks for reminding me of what I probably learned once upon a time, but forgot (sigh).

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PostPosted: Wed Nov 30, 2005 8:22 am 
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Darell C. Phillips wrote:
The thing that bothers me just a bit is that if indeed Gravity is pretty much the same speed as c is, doesn't this contradict instantaneous action at a distance, which seems to be accepted in order to keep the planets in orbit?

No, not under general relativity. This is mentioned in the link you quoted:
http://math.ucr.edu/home/baez/physics/R ... speed.html :wink:


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PostPosted: Wed Nov 30, 2005 8:26 am 
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Darell C. Phillips wrote:
I still wish there was some way to break through "Einstein's Wall".

Oh, if it's faster-than-light travel you are desiring, there are much better candidates than Weber's sails.

http://www.projectrho.com/rocket/rocket3v.html#existing
(be sure to scroll to the top to read the discussion of the theoretical problems with FTL)
I'm surprised you haven't heard of Dr. Alcubierre's infamous "warp drive."


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PostPosted: Wed Nov 30, 2005 8:29 am 
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Winchell Chung wrote:
Well, it is my understanding that the vast majority of physicists are of the opinion that the speed of gravity is no more than c. And I tend to trust the New Scientist website more than a web site called "gravityWarpDrive" :roll:

And while math is perfect, its application is not. Math, like logic, is about the validity of the process. It cannot be used to determine if something is true or false.

Logic states that the following is in proper logical form: if A is equal to B, and B is equal to C, therefore A is equal to C.

So the following is perfectly logical: If women are slaves and Betty is a woman, therefore Betty is a slave. It is also utterly false.

Like they used to say in computer programming: Garbage In, Garbage out.

The way to determine the truth is by the scientific method. Which include doing experiments, like the one Mr. Zebrowski mentioned.


I hate to say it, dude, but logic and math CAN be used to prove something absolutely true or absolutely false, based on a set of assumptions. Your comment on the example for the transitive property of equality isn't correct; if both of the pre-conditions are true, then the conclusion is true. If the conclusion is false, then one or both of the pre-conditions is false. The reason your statement is false is because the pre-condition "All women are slaves" is false; hardly any are in the modern world.

It's also worth noting that your example is more appropriate for implication (a->b and b->c means a->c) than equality, but that's a minor point. Using it as an example for the transitive property of equality includes the implied baggage that all slaves are women.

In general, when trying to make an example for something like this, I've always found it easier to use examples with less emotional baggage attached. A favorite of mine and of my fellow math majors was "All apples are red; this thing in my hand is an apple; therefore, this thing in my hand is red." Logically, it's a perfectly true statement; in practice, it's a false statement, because one of the pre-conditions ("all apples are red") is false.

Anyway. I digress.

The entire POINT of math and logic is to prove something true, false, or unproveable. If a mathematical proof turns out to be false, then it's because of an error either in the assumptions or the process, not in math. In the case of physics, every time something "proven" has ended up being false, it's been because of a false assumption (they assumed something was a constant when it was actually variable with distance, or they assumed space-time was a flat plane when it is actually bent by the presence of objects, or something similar), or because they missed an assumption entirely and the proof is actually a special case of a generic principle.


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 Post subject: Split this off...
PostPosted: Wed Nov 30, 2005 11:16 am 
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We have a topic area for science questions.

James, please move these messages over to it, with a subject of Speed of Gravity?

Thanks.

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PostPosted: Wed Nov 30, 2005 2:05 pm 
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Winchell Chung wrote:
Darell C. Phillips wrote:
The thing that bothers me just a bit is that if indeed Gravity is pretty much the same speed as c is, doesn't this contradict instantaneous action at a distance, which seems to be accepted in order to keep the planets in orbit?

No, not under general relativity. This is mentioned in the link you quoted:
http://math.ucr.edu/home/baez/physics/R ... speed.html :wink:


OK Winch, I just needed to reread that. Thanks for being so gentle with me :oops: . Although I would love to see an animation describing the apparent contradiction (and then explain how it isn't a contradiction really), I can now accept that Gravity is basically the same speed as Light. The New Scientist article's finding (Ed Fomalont) was that Gravity was .95 c (not including the error factor), and the UC Riverside site had it within c by 1%.

Also, poking a bit further I found another perspective on Gravity that was interesting. Here is a quote from a FAQ page:

"Is gravity itself a fictitious force?
A few lines up, I wrote that the force we feel when the bus is braking, is weird in that its strength is proportional to our own mass. But what about gravity? That also has a strength that is proportional to our mass! Could gravity be a fictitious force too?

Yes, that's exactly how gravity is viewed these days. This is the content of Einstein's General theory of Relativity. Einstein conjectured that perhaps we've been looking at things in the wrong way. Newton viewed the orbit of a satellite, or the parabolic flight of a projectile, or the fall of an apple, to be complicated motions caused by the action of this mysterious force called gravity. But Einstein turned the problem on its head, and decided that satellites, projectiles, and apples are all following a motion that is as simple as any motion can be, provided they are viewed on the stage of a curved spacetime. The ones whose motion through spacetime is very complicated are ourselves, standing on Earth's surface.

This change of view wasn't just made for the sake of a different viewpoint. Einstein's change in viewpoint enabled him to make predictions that differ to corresponding ones made by Newton's theory. And it's Einstein's predictions that have been verified experimentally to a very high accuracy.

So gravity can be treated as a fictitious force. But it's a sort of "higher order" fictitious force when compared to the everyday one we experience in a bus: unlike the very uniform force that pushes us forward in a braking bus, gravity can't be made to completely vanish by a simple change of frame. Added to that, the mathematics of curved spacetimes is more complicated than using F=ma. So for everyday uses, it's completely sufficient to treat gravity as a good old real force, just like the mechanics books tell us to do."

Here is the source site: http://math.ucr.edu/home/baez/physics/G ... entri.html

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 Post subject: Re: Split this off...
PostPosted: Wed Nov 30, 2005 2:52 pm 
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Ken Burnside wrote:
We have a topic area for science questions.

James, please move these messages over to it, with a subject of Speed of Gravity?

Thanks.


Thanks, Ken. I just knew I was going to get in trouble for this mischief :wink:

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PostPosted: Wed Nov 30, 2005 3:54 pm 
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Winchell Chung wrote:
Darell C. Phillips wrote:
I still wish there was some way to break through "Einstein's Wall".

Oh, if it's faster-than-light travel you are desiring, there are much better candidates than Weber's sails.

http://www.projectrho.com/rocket/rocket3v.html#existing
(be sure to scroll to the top to read the discussion of the theoretical problems with FTL)
I'm surprised you haven't heard of Dr. Alcubierre's infamous "warp drive."


Winch, you have amassed a great deal of information from a variety of sources (meaning I love it!). I wish I had more time to absorb it all. No, I hadn't heard of Dr. Alcubierre's ideas. It's great to know there are a few loose bricks in Dr. Einstein's "wall". What I did in my old game was to throw Niven and Pournelle's Alderson drive, Wormholes, Negative Energy, and a few other things into a blender. What I ended up with was a sort of intersteller LaGrange point that needed a "can opener" (installed in a ship of course). A negative energy field was created (at a fixed point from a star), and the ship "slipped" through the shortcut and into a reciprocal point in the target star system. I had two tactical hex map scales (inner and outer systems and each containing "our" inner and outer planets). On the outer scale map, I would superimpose a third map of "strategic" space showing the positions of the stars. These "stars" would be the locations of my "SLIP" locations (Super-Luminary Initial Points). The points would be in a direct line between the two stars, but not all stars' points of access would be available. This was based on the strength of the ship's stardrive (as in how big a can opener was needed). The entry threshold was a number derived from the ratio between the mass of the local star and the target star. This obviously made being at a small star very good, as it allowed more destinations and at greater distances. I was fairly proud of my "mix" for resolving strategic movement and which star systems became chokepoints. The most valuable were binary systems with a "Laurel and Hardy" pair of stars. You had to be careful, because you could go to a large star very easily, but the very thing that made it easy to get there would also trap you from going back (unless you could line up between a local "Laurel" star and a new distant "Hardy" to escape. If you arrived at a "Hardy" that was a lone star, you shouldn't have made the trip, because you've come to a dead end "sump" and you better like it there because you're staying for awhile :shock: . Anyway, I liked my PSB method, for me. It was kind of gliding on a wire between stars, with the larger star pulling you toward it.

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